Oil: what do you use?

[— kung fu jesus —]

Honestly, I drive a 93 miata with 96k on it. It was made in 1992. 20 years ago we didnt have nearly as fancy synthetic oils as we do today, and the car was designed with clearances for conventional motor oil. After 96k miles of (i'm assuming, because it was an older woman who seemed to maintain the car, but not go above and beyond) generic jiffy lube type oil changes, I stick to my cheap oil. And I mean I walk into (insert autoparts store here) and buy whatever is on sale that week. This week it was 5 qts of quaker state conventional and a driveworks filter for $17.95.

The problem with switching to synthetic is the particles are not similar in size to conventional. Think of conventional particles like this : ooO0oo0oo0o0oOOO0o and synthetic like this: ooooooooooooo. The more uniformly smaller particles find their way out of any and all wear in any gaskets or o-rings etc. Also there is always the chance that the bearings and such are worn and the synthetic is too thin to lubricate properly. Under extreme forces (most often track driving) this can kill an engine.

All this being said, when I do build a motor for the miata I will break it in on full synthetic and run a high quality synthetic in it every oil change.

Hmm, that is a bit antiquated. I can assure you my '92 saw nothing but synthetic. Two turbo systems, a supercharger, and track time well over 40 hours. After 165k I scoped the cylinders. No scoring, cross-hatching intact. Bearing surfaces on the head were within spec and zero signs of varnish on the castings or HLAs. Oil is cheap, even synthetic, engine repairs are not.

[AntiochOG]

Mobil 1 Fully Synthetic 0W-30

[PHEOX]

Rotella. Just switched to it and all of my leaks are showing quite more than before. No issue to me, getting all seals replaced in a couple of weeks.

[Ihatecars]

Apparently I'm a psychopath, but I use 10W-30 Royal Purple. I've used it in everything expect for my Rx-7(Synthetic+Rotary=Not that good of an idea) without any problems.
Oh, and I used a lighter weight(5w-30 typically) last winter in the Ka my 240sx had. Might do the same for the roadster this winter.

[—atank—]

Mobil 1

[iamdallas]

Rotella T6.